Do quiescent and active galaxies have different M_BH-sigma relations?

Abstract

To investigate the validity of the assumption that quiescent galaxies and active galaxies follow the same black hole mass - stellar velocity dispersion relation, as required for the calibration of M_BH estimators for broad line AGNs, we determine and compare the M-sigma relations, respectively, for quiescent and active galaxies. For the quiescent galaxy sample, composed of 72 dynamical M_BH measurements, we update sigma for 28 galaxies using homogeneous H-band measurements that are corrected for galaxy rotation. For active galaxies, we collect 25 reverberation-mapped AGNs and improve sigma measurement for two objects . Combining the two samples, we determine the virial factor $f$, first by scaling the active galaxy sample to the M-sigma relation of quiescent galaxies, and second by simultaneously fitting the quiescent and active galaxy samples, as f=5.1_{-1.1}^{+1.5} and f=5.9_{-1.5}^{+2.1}, respectively. The M-sigma relation of active galaxies appears to be shallower than that of quiescent galaxies. However, the discrepancy is caused by a difference in the accessible M_BH distribution at given sigma, primarily due to the difficulty of measuring reliable stellar velocity dispersion for the host galaxies of luminous AGNs. Accounting for the selection effects, we find that active and quiescent galaxies are consistent with following intrinsically the same M-sigma relation.